This invention relates to an improved, fully sealed piston ring structure particularly adapted for use in high pressure engines and pumps, and to a method for fabricating such ring structure.
This invention further relates to an improvement of piston rings of the type described in my prior U.S. Pat. No. 2,670,255 issued Feb. 23, 1954.
In internal combustion gasoline engines for a typical present day passenger car, the engine pistons are provided with two compression rings and one oil ring. The compression rings are conventionally unitary rings which are split and have adjacent abutting ends. In the assembly of these rings onto the piston and into an engine, some clearance must be provided between the adjacent ends to allow for therman expansion. Necessarily then there is a gap between the adjacent ends of each ring which presents a direct path for gases from one side of the ring to the other. An oil ring defines an expansion gap in the same manner. The result of this is that, even though the three rings are in series, there is a direct path for gases to flow between the cylinder compression chamber and the base of the piston, which is of course open to the crank case. This direct path results in losses in the engine efficiency and increases the pollution of the air due to exhaust emissions and crank case ventilation for the following reasons.
In regard to reduction of engine efficiency the degree of compression of the air, or air-fuel mixture, on the compression stroke is less than it should be for the reason that, during the compression stroke, some of the compressed gases flow past the piston rings into the crank case. Similarly, on the power stroke of the piston some of the expanding gases are blown past the piston into the crank case thereby not producing useful work on the head of the piston. It has been estimated by automotive people that, even with the best available piston rings of the type above mentioned, there is a minimum 10 to 15 percent loss of compression.
This path between the cylinder chamber and crank case increases contamination or pollution of the air for the following reasons. First, with the above mentioned loss of efficiency additional fuel is necessarily consumed to compensate for the loss of efficiency resulting in additional exhaust emissions. Secondly, on the suction stroke of the piston where the cylinder chamber pressure is less than that in the crank case, oil and vapors from the crank case will be drawn into the cylinder chamber to be subsequently compressed on the compression stroke with the fuel oil mixture and burned on the power stroke. This of course contaminates the fuel air mixture and produces unburned hydrocarbonns which are then discharged through the exhaust system. Furthermore the flow of gases into the crank case during the compression and power strokes results in contamination and vapors in the crank case which are subsequently drawn back into the cylinder chamber from the crank case on the suction stroke.
To obviate these problems, fully sealed compression rings are desirable. Possibly why one reason such fully sealed rings have not been made available in conventionanl automobile engines is that the expense of manufacture is considerably greater than that for the above mentioned conventional unitary compression rings. Therefore what this invention contemplates is the production of fully sealed, precision manufactured rings which may be used in conventional passenger engines but which may be manufactured readily and rapidly at a reasonable cost.
An object of this invention is to provide an improved piston ring assembly, and method of manufacture, which substantially eliminates both radial and axial blowby.
Another object of this invention is to provide an improved, fully sealed piston ring assembly providing extremely close contact with a cylinder wall.
A further object of this invention is to provide a piston ring assembly, and method of manufacture, for use in a single piston groove which is far superior to a single piston ring, yet which may be manufactured expeditiously and economically.
A still further object of this invention is to provide a fully sealed piston ring assembly capable of economic yet precision manufacture, and a method of manufacture therefor.
Still another object of this invention is to provide a fully sealed piston ring assembly capable of economic yet precision manufacture, and method of manufacture therefore, consisting of side-by-side rings with a tab and recess antirotation coupling, wherein the tab is an integral part of the respective ring member.
These objects are accomplished in a ring assembly manufactured according to the following steps: forming first and second split compression ring members with parallel side surfaces and generally cylindrical peripheral edge surfaces, dimensioned for side-by-side mating relation; forming circumferentially overlapping radially contiguous tongues in the ends of each ring member, with radially confronting sealing surfaces; forming an index tab integral with said first ring member by deforming a portion of the ring material, intermediate its ends and intermediate its edges, to produce a boss projecting laterally from one side thereof and having a sharp intersection with said side surface; forming a recess in one side of said second ring member, intermediate its ends and intermediate its edges, dimensioned to receive said boss with lateral clearance, to permit limited relative sliding movement of said first and second ring members in side-by-side relation; positioning said boss and said recess, on said respective first and second ring members, to maintain the joints of the mated ring members in rotationally spaced relation to each other; and finishing the confronting sides of said ring members to be fully contiguous in assembled mated relation.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.